When I use a transparent PNG as a texture in Blender, the parts that should be transparent are rendered as black.

This is especially confusing since in the material preview it looks as if the material would indeed be transparent.

Here's a screenshot:

This is the test texture, and in the right on top of a checkerboard:

Here is the .blend file in case you want to check it:

Edit: After playing with the settings, it does render with transparency in the rendered output, but that's not what I need. I want to use the models with Three.js, so I want to just quickly see how it looks in Blender, I don't need more than simple "Z-transparency" ("regular" one, non-raytraced) here's a reference rendering of what I expect to see in Blender while I edit (this is the same model rendered with Three.js on an HTML <canvas>):

@CamiloMartin - How did you make the I'm actually a .zip file thing?
–
Derek 朕會功夫Jun 21 '13 at 5:11

1

@Derek朕會功夫 - Cool isn't it? :D cat file.png file.zip > mix.png on Unix, and copy /B file.png file.zip mix.png on Windows. This works because 7-Zip (and many other programs) will look for the zip header (or any other valid header that it supports), even if it's not at the beginning. For this reason you can open .docx, installers, and a number of proprietary-format files straight in 7-Zip. The image itself was self-made.
–
Camilo MartinJun 21 '13 at 17:31

1

Oh, and by the way, the image is public domain, in case you want it you're free to use it too. Here it is, ready to be concatenated with whatever zip: i.imgur.com/1cHoKa4.png
–
Camilo MartinJun 22 '13 at 5:14